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avon roadrider

posplayr said:
Well you may have a point there, but I'm struggling with how a wider tire will not generate a larger contact patch??
Click to expand...
A wider tire (than the bike is designed for) is designed to be put on a wider rim, as well. If you squeeze it down onto a narrow rim, it will be forced into a tighter radius, which will reduce the contact patch.

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Steve said:
A wider tire (than the bike is designed for) is designed to be put on a wider rim, as well. If you squeeze it down onto a narrow rim, it will be forced into a tighter radius, which will reduce the contact patch.

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Click to expand...

No, it will flex the casing more to reach the same contact patch - with a slight adjustment for casing stiffness.

Let me repeat, a wider tire does not have a larger contact patch. It will have a more gentle radius and more available surface area, but the amount you are using at any one time is pretty much a function of air pressure, unless you've got a really stiff, kludgy casing. In general, you can run a wider tire at a lower pressure and - bingo - larger contact patch. A wider - read more gentle radius - tire will tend to generate a wider contact patch as the pressure drops; narrow, tight radius adds length faster. For cornering, a wider contact patch is probably more effective but the freedom of design afforded by modern construction to use softer rubber compounds is responsible for most of the traction increase.

Actually, wide tires can be made for narrow rims - see mountain bikes - just by continuing the sidewall further around the circle. But the angle at the bead gets pretty kooky and the 'waddle factor' from lack of lateral support may get out of hand. If you want to get into radial/belted designs, the short sidewall/wide rim is how it is.

If you look at Moto GP and Moto 3 bikes - 1 liter and 250cc respectively - you see the small bikes using a skinny rear but the riders still dragging their elbows and mid corner speeds being almost the same. The fronts aren't that much different as the bikes don't weigh all that much different. But the big motors would shred the skinny rear tire almost immediately. Entering the corners, the back wheel is almost off the road and the front contact patch is doubled; leaving is the opposite with total transfer to the rear. If you're going to transfer all the weight to the back and apply massive hp at major speeds, a 4.00 18 isn't really capable; well, not for long.
 
An excerpt from Motorcycle Industry Council Tire Guide and some good reading on motorcycle tires:

http://www.mic.org/downloads/mic_tire_guide_2012v1.pdf

Because a motorcycle is a single-track vehicle and leans as it turns, motorcycle tires are quite different than car tires. Whereas car tires have a fairly flat profile and a contact patch that varies little in size or shape, motorcycle tires have a U-shaped profile and a contact patch that changes size and shape during cornering. Motorcycle tires are also relatively narrow, which makes their gripping capability (“traction”) a limited commodity.



 
JTGS850GL said:
An excerpt from Motorcycle Industry Council Tire Guide and some good reading on motorcycle tires:

http://www.mic.org/downloads/mic_tire_guide_2012v1.pdf

Because a motorcycle is a single-track vehicle and leans as it turns, motorcycle tires are quite different than car tires. Whereas car tires have a fairly flat profile and a contact patch that varies little in size or shape, motorcycle tires have a U-shaped profile and a contact patch that changes size and shape during cornering. Motorcycle tires are also relatively narrow, which makes their gripping capability (?traction?) a limited commodity.
Click to expand...

I'd hate to depend upon whatever else this guy wrote. He seems to be under the impression that a motorcycle tire can magically turn the lateral cornering forces about 45 degrees and turn them into downforce. Vector voodoo.

Actually, the contact patch on an outside car tire changes during cornering, but that's from weight transfer from the inside tires. All we got is outside tires.

And traction is always a limited commodity. I hope he knows that?.

So I think he's wrong. Did he go on any longer?
 
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